1. Field of the Invention
The present invention relates to an internal combustion engine provided with a combustion heater for elevating a temperature of an engine related element such as cooling water or intake air.
2. Description of the Related Art
In an internal combustion engine to be mounted on an automotive vehicle or the like, in particular, an internal combustion engine such as a diesel engine in which a heat quantity is likely to be small, a technique to additionally provide a combustion heater for the purpose of acceleration of warming up the internal combustion engine or enhancement of a passenger room heating device in a cold state.
The above-described combustion heater is provided with a combustion chamber which is independent of the internal combustion engine. Furthermore, the combustion heater is provided with a heat exchange portion composed of a water path formed so as to surround the combustion chamber.
The water path (water path in the heater) of the above-described heat exchanger and a cooling path of the internal combustion engine are in communication with each other through a cooling water leading path for introducing the cooling water from the cooling path of the internal combustion engine to the water path in the heater and a cooling water discharge passage for introducing the cooling water from the water path in the heater to the cooling path of the internal combustion engine. A heater core of the passenger room heating device is provided in the midway of the cooling water discharge passage.
In the thus constructed combustion heater, a part of fuel of the internal combustion engine is burnt in the combustion chamber in a cold state or the like of the internal combustion engine, and at the same time, the cooling water for the internal combustion engine is introduced to the water path in the heater through the cooling water leading path.
In this case, the heat generated as a result of the combustion within the combustion chamber is transferred to the cooling water in the heat exchanger portion to elevate the temperature of the cooling water. The cooling water (hot water) which has been heated in the heat exchange portion is discharged from the water path in the heater to the cooling water discharge passage to be returned back to the cooling water path through the heater core. When the above-described hot water has passed through the heater core, a part of heat of the hot water is transferred to the heating air that flows through the heater core, thereby the temperature of the heating air being elevated.
According to the above-described combustion heater, it is possible to elevate the temperature of the heating air or the engine cooling water in an earlier stage in the cooling operation of the internal combustion engine and it is possible to enhance the acceleration of the warmup of the engine and the heating capacity.
However, in the combustion heater, since the combustion is conducted by utilizing the part of the fuel for the internal combustion engine, there are cases where the burnt gas emitted from the combustion heater contains harmful gas components like the emission of the internal combustion engine. In those cases, it is necessary to discharge the emission after purifying the harmful gas components contained in the burnt gas.
In order to meet such a requirement, Japanese Patent Application Laid-Open No. Sho 60-78819 describes xe2x80x9cHEATING DEVICE FOR A VEHICLE PROVIDED WITH A COMBUSTION HEATERxe2x80x9d. In the heating device disclosed in this publication, an exhaust port of a heater exhaust pipe for discharging the gas burnt in the combustion heater is provided upstream of the exhaust gas purifying device of the exhaust pipe of the internal combustion engine, and the burnt gas to be discharged from the combustion heater is introduced into the exhaust gas purifying device for the internal combustion engine to thereby purify the harmful gas components contained in the burnt gas with the exhaust gas purifying device for the internal combustion engine.
It is possible to exemplify a three-element catalyst, an adsorption reduction type lean NOx catalyst, a selective reduction type lean NOx catalyst or the like for the exhaust gas purifying device of the internal combustion engine. However, since these exhaust gas purifying devices are activated so that the harmful gas components contained in the exhaust gas may be purified when the catalyst bed temperature exceeds a predetermined level, in order to positively purify the burnt gas from the combustion heater and the exhaust gas from the internal combustion engine, it is necessary to keep the exhaust gas purifying devices at the activation temperature or more.
However, in the case where the internal combustion engine is a diesel engine, a heat generation amount of the internal combustion engine tends to be small in a low load operational region, and the exhaust gas temperature is likely to be low. Accordingly, it is difficult to keep the exhaust gas purifying device at the activation temperature or more only by the exhaust gas of the internal combustion engine.
In contrast, as in Japanese Patent Application Laid-Open No. Sho 60-78819 entitled xe2x80x9cHEATING DEVICE FOR A VEHICLE PROVIDED WITH A COMBUSTION HEATERxe2x80x9d, it is possible to propose that the burnt gas that is relatively high in temperature from the combustion heater is introduced into the exhaust gas purifying device to thereby elevate the temperature of the exhaust gas purifying device. However, since the temperature of the exhaust gas to be discharged from the above-described combustion heater is lowered by the heat exchange with the heating air in the heat exchange portion, there is a problem in that it takes long time to elevate the temperature of the exhaust gas purifying device up to the activation temperature, and the exhaust emission would become worse in the meantime.
In order to overcome the above-noted defects, an object of the present invention is to provide a technique that may provide an internal combustion engine provided with a combustion heater for elevating a temperature of an engine related element by supplying a burnt gas having a large heat quantity to an internal engine of an exhaust gas purifying device, to thereby effectively perform temperature elevation of the exhaust gas purifying device and warmup acceleration of the internal combustion engine.
In order to attain the above-described object, the present invention adopts the following means.
Namely, an internal combustion engine with a combustion heater according to the present invention, comprises:
an exhaust gas purifying catalyst provided in an exhaust passage of the internal combustion engine for purifying harmful gaseous components contained in exhaust gas;
a combustion heater including a combustion chamber that is independent of the internal combustion engine and a heat exchange portion for transmitting to an engine related element heat held by burnt gas that has been burnt in the combustion chamber;
a first burnt gas discharging means for discharging from the combustion heater the burnt gas which has passed through the heat exchange portion;
a second burnt gas discharging means for discharging from the combustion heater the burnt gas that has not yet passed through the heat exchange portion or that has passed through a part of the heat exchange portion; and
a burnt gas passage controlling means for communicating at least one of the first burnt gas discharging means and the second burnt gas discharging means with a portion upstream of the exhaust gas purifying catalyst in the exhaust passage.
In the thus constructed internal combustion engine with a combustion heater, the relatively low temperature burnt gas through the heat exchange portion in the combustion heater and the relatively high temperature burnt gas that has not passed through the heat exchange portion are fed to the exhaust passage upstream of the exhaust gas purifying catalyst as desired.
For example, in the case where the temperature of the engine related element is to be elevated, the burnt gas passage controlling means communicates the first burnt gas discharging means and the exhaust passage upstream of the exhaust gas purifying catalyst with each other. In this case, the burnt gas that has been burnt in the combustion chamber of the combustion heater has passed through the heat exchange portion and thereafter is fed to the exhaust passage through the first burnt gas discharging means. While the burnt gas passes through the heat exchange portion, the heat of the burnt gas is transmitted to the engine related element to elevate the temperature of the engine related element.
Also, in the case where the temperature of the exhaust gas purifying catalyst is to be elevated, the burnt gas passage controlling means communicates the second burnt gas discharging means and the exhaust passage upstream of the exhaust gas purifying catalyst with each other. In this case, the burnt gas that has not passed through the heat exchange portion is fed to the exhaust passage through the second burnt gas discharging means. Since the burnt gas that has not passed the heat exchange portion has a high temperature in comparison with the burnt gas that has passed through the heat exchange portion, if such a high temperature burnt gas is fed to the exhaust passage upstream of the exhaust gas purifying catalyst, the temperature of the exhaust gas purifying catalyst is elevated earlier.
Incidentally, the above-described internal combustion engine with a combustion heater may further comprise an intake throttle valve for reducing an amount of intake air flowing through an intake passage of the internal combustion engine if the second burnt gas discharging means is in communication with the portion upstream of the exhaust gas purifying catalyst in the exhaust passage.
The reason for this is that, in an internal combustion engine such as a diesel engine in which a combustion temperature is low in a low load operational region and an exhaust gas temperature is likely to be low, since there are cases that the exhaust purifying catalyst is cooled by the low temperature exhaust gas, it is necessary to reduce the exhaust gas amount to be discharged from the internal combustion engine by reducing the intake air amount of the internal combustion engine in order to elevate the temperature of the exhaust gas purifying catalyst.
As the internal combustion engine with a combustion heater according to the present invention, it is possible to exemplify one provided an intake air introducing passage for introducing the air for combustion from the intake passage to the combustion chamber of the combustion heater. In the case where a supercharger is provided in the intake passage of the internal combustion engine, it is preferable that the above-described intake air introducing passage is connected to a portion downstream of the supercharger in the intake passage.
The reason for this is that, since there are some cases that the pressure of the intake passage upstream of the supercharger is lower than the pressure of the exhaust passage upstream of the exhaust gas purifying catalyst, when the intake air introducing passage is connected to the portion upstream of the supercharger in the intake passage, it is assumed that the exhaust gas flowing through the exhaust passage upstream of the exhaust gas purifying catalyst is caused to reversely flow from the first burnt gas discharging means or the second burnt gas discharging means through the combustion heater and the intake air introducing passage to the intake passage.
Next, an internal combustion engine with a combustion heater according to the present invention may comprises:
a combustion heater including a combustion chamber that is independent of the internal combustion engine and a heat exchange portion for transmitting to an engine related element heat held by burnt gas that has been burnt in the combustion chamber;
a first burnt gas discharging means for discharging from the combustion heater the burnt gas which has passed through the heat exchange portion;
a second burnt gas discharging means for discharging from the combustion heater the burnt gas that has not yet passed through the heat exchange portion or that has passed through a part of the heat exchange portion;
an intake air introducing passage for introducing air for combustion from an intake passage of the internal combustion engine to the combustion heater;
a first burnt gas passage for communicating the first burnt gas discharging means with a joint portion downstream of the intake air introducing passage in the intake passage;
a second burnt gas passage for communicating the second burnt gas discharging means with a joint portion downstream of the first burnt gas passage in the intake passage; and
a burnt gas passage controlling means for controlling of a flow of gas in the second burnt gas passage.
In this case, it is preferable that the joint portion between the intake passage and the second burnt gas passage is selected to a position where the pressure may be lower than that of the joint portion of the first burnt gas passage and that of the intake passage introducing passage in the intake passage.
In the case where the supercharger is provided in the intake passage of the internal combustion engine, it is preferable to provide the intake air introducing passage downstream of the supercharger.
In the thus constructed internal combustion engine with a combustion heater, the burnt gas passage controlling means communicates the second burnt gas passage when a temperature of the body of the engine or a temperature of the engine related element is to be elevated.
In this case, since the intake air introducing passage, the first burnt gas passage and the second burnt gas passage are in communication, applied to the combustion heater are the pressure in the vicinity of the joint portion of the intake air introducing passage in the intake passage, the pressure in the vicinity of the joint portion of the first burnt gas passage in the intake passage and the pressure in the vicinity of the joint portion of the second burnt gas passage in the intake passage.
The pressure of the pressure in the vicinity of the joint portion of the second burnt gas passage in the intake passage is lower than the pressure in the vicinity of the joint portion of the intake air introducing passage in the intake passage and lower than the pressure in the vicinity of the joint portion of the first burnt gas passage in the intake passage. For this reason, the air is introduced from the intake passage through the intake air introducing passage to the combustion heater and at the same time the air is introduced from the intake passage through the first burnt gas passage to the combustion heater. The air that has been introduced through the intake air introducing passage and the first burnt gas passage to the combustion heater is discharged through the second burnt gas exhaust means and the second burnt gas passage to the intake passage.
Here it should be noted that the combustion heater is provided with a gas passage for introducing the air from the intake air introducing passage to the combustion chamber and subsequently introducing the air from the combustion chamber to the heat exchange portion, the first burnt gas discharging means is constructed to discharge the burnt gas from the gas flow passage downstream of the heat exchange portion, and the second burnt gas discharging means is constructed to discharge the burnt gas from,the gas flow passage upstream of the heat exchange portion.
The air that has been introduced into the combustion heater through the intake air introducing passage reaches the second burnt gas discharging means through the combustion chamber (The air reaches the combustion chamber from the intake passage through the intake air introducing passage will hereinafter be referred to as the air for combustion). The air that has been introduced into the combustion heater through the first burnt gas passage reversely flows through the heat exchange portion and reaches the second burnt gas discharging means (The air that reaches the second burnt gas discharging means through the heat exchange portion and the first burnt gas discharging means from the intake passage will hereinafter be referred to as secondary air).
If the above-described secondary air is fed to the second burnt gas discharging means located downstream of the combustion chamber, even if the pressure difference between the joint portion of the second burnt gas passage and the joint portion of the intake air introducing passage in the intake passage is increased, the pressure difference between the upstream side and the downstream side of the combustion chamber is suppressed. As a result, the flow rate and the flow amount of the gas passing through the combustion chamber are not increased excessively and the combustion within the combustion chamber is stabilized.
Also, in the combustion heater, the air for combustion introduced into the combustion chamber is burnt together with predetermined fuel. The burnt gas that has been burnt in the combustion chamber is discharged from the combustion chamber to the gas flow path. At this time, since the burnt gas is prevented from entering the heat exchange portion by the secondary air reversely flowing the heat exchange portion, the burnt gas reaches the second burnt gas discharging means without passing through the heat exchange portion. Accordingly, the burnt gas discharged from the combustion chamber is not used for heat exchange with the engine related element and the heat quantity of the burnt gas is increased.
Subsequently, the second burnt gas discharging means discharges the mixture gas of the above-described secondary gas and burnt gas. The burnt gas that has been discharged from the second gas burnt gas discharging means is fed to the intake passage through the second burnt gas passage. The mixture gas fed to the intake passage is introduced into the internal combustion engine through the intake passage.
Since the above-described mixture gas has the heat quantity that is substantially equal to that of the burnt gas but has a lower temperature than that of the burnt gas, none of the second burnt gas discharging means, the second burnt gas passage and the burnt gas passage controlling means or the like are not excessively elevated. Furthermore, the atmospheric temperature within the sleeve of the internal combustion engine is elevated by the relatively large heat quantity possesses by the mixture gas.
Incidentally, as described above, in the case where the intake air introducing passage, the first burnt gas passage and the second burnt gas passage are connected in order from the upstream side to the downstream side of the intake passage, it is possible to provide an intake throttle valve between the joint portion of the first burnt gas passage in the intake passage of the internal combustion engine and the joint portion of the second burnt gas passage in the intake passage of the internal combustion engine for adjusting a flow rate of the intake air flowing through the intake passage.
With such an arrangement, by throttling the opening degree of the intake throttle valve after the start of the internal combustion engine in the cold start of the internal combustion engine (in cranking) or the like, the joint portion of the second burnt gas discharging passage in the intake passage may be kept at a lower pressure than that of the joint portion of the intake air introducing passage and the joint portion of the first burnt gas passage in the intake passage.
In this case, the air for combustion is fed from the intake passage through the intake air introducing passage into the combustion heater, and at the same time, the secondary air is fed from the intake passage through the first burnt gas passage into the combustion heater. The combustion heater discharges the mixture of the burnt gas having a large heat quantity and the secondary air having a high oxygen concentration to the intake passage through the second burnt gas passage.
As a result, it is possible to keep the necessary amount of oxygen for the engine combustion by the oxygen contained in the secondary air in the mixture gas while elevating the temperature of the atmosphere within the sleeve of the internal combustion engine by the heat held by the burnt gas in the above-described mixture gas.
The internal combustion engine with a combustion heater according to the present invention, the burnt gas passage controlling means also communicates the second burnt gas passage when temperature elevation demand of an exhaust gas purifying catalyst provided in the exhaust passage of the internal combustion engine occurs.
In this case, the combustion heater discharges the mixture gas of the secondary air and the burnt gas having the large heat quantify. The mixture gas is fed through the second bunt gas passage to the intake passage.
As a result, it is possible to elevate the intake air temperature while preventing the thermal damage of the internal combustion engine body or the intake system of the internal combustion engine to thereby elevate the exhaust gas temperature of the internal combustion engine to elevate the temperature of the exhaust gas purifying catalyst.
In this case, if the amount of the intake air of the internal combustion engine is decreased by the intake throttle valve, even if the amount of the gas discharged from the combustion heater is small, it is impossible to sufficiently elevate the temperature of the intake air and to reduce the amount of fuel consumption for the operation of the combustion heater.
Next, an internal combustion engine with a combustion heater according to the present invention may comprise:
an exhaust gas purifying catalyst provided in an exhaust passage of the internal combustion engine for purifying harmful gaseous components contained in exhaust gas;
a combustion heater including a combustion chamber that is independent of the internal combustion engine and a heat exchange portion for transmitting to an engine related element heat held by burnt gas that has been burnt in the combustion chamber;
a first burnt gas discharging means for discharging from the combustion heater the burnt gas which has passed through the heat exchange portion;
a second burnt gas discharging means for discharging from the combustion heater the burnt gas that has not yet passed through the heat exchange portion or that has passed through a part of the heat exchange portion;
an intake air introducing passage for introducing air for combustion from an intake passage of the internal combustion engine to the combustion heater;
a first burnt gas passage for communicating the first burnt gas discharging means with a joint portion downstream of the intake air introducing passage in the intake passage;
a second burnt gas passage for communicating the second burnt gas discharging means with an exhaust passage upstream of the exhaust gas purifying catalyst; and
a burnt gas passage controlling means for controlling of a flow of gas in the second burnt gas passage.
In this case, it is preferable that the joint portion the second burnt gas passage in the intake passage is selected to a position where the pressure may be lower than that of the joint portion of the first burnt gas passage and that of the intake passage introducing passage in the intake passage.
Also, in the case where the supercharger is provided in the intake passage of the internal combustion engine, it is preferable to provide the intake air introducing passage downstream of the supercharger.
The internal combustion engine with a combustion heater according to the present invention, the burnt gas passage controlling means communicates the second burnt gas passage when temperature elevation demand of an exhaust gas purifying catalyst provided in the exhaust passage of the internal combustion engine occurs.
In this case, since the intake air introducing passage, the first burnt gas passage and the second burnt gas passage are in communication, applied to the combustion heater are the pressure in the vicinity of the joint portion of the intake air introducing passage in the intake passage, the pressure in the vicinity of the joint portion of the first burnt gas passage in the intake passage and the pressure in the vicinity of the joint portion of the second burnt gas passage in the intake passage.
The pressure of the pressure in the vicinity of the joint portion of the second burnt gas passage in the intake passage is lower than the pressure in the vicinity of the joint portion of the intake air introducing passage in the intake passage and also lower than the pressure in the vicinity of the joint portion of the first burnt gas passage in the intake passage. For this reason, the air for combustion is introduced from the intake passage through the intake air introducing passage to the combustion heater and at the same time the secondary air is introduced from the intake passage through the first burnt gas passage to the combustion heater.
The above-described air for combustion is introduced into the second burnt gas discharging means through the combustion chamber of the combustion heater. The above-described secondary air is caused to reversely flow through the heat exchange portion and to be introduced into the second burnt gas discharging means. Thus, if the secondary air is fed to the second burnt gas discharging means located downstream of the combustion chamber, even if the pressure difference between the joint portion of the third burnt gas passage in the exhaust passae and the joint portion of the intake air introducing passage in the intake passage is increased, the pressure difference between the upstream side and the downstream side of the combustion chamber is suppressed. As a result, the flow rate and the flow amount of the gas passing through the combustion chamber are not increased excessively and the combustion within the combustion chamber is stabilized.
Also, in the combustion heater, since the burnt gas that has been discharged from the combustion chamber is prevented from entering the heat exchange portion by the secondary air reversely flowing in the heat exchange portion, the heat of the burnt gas is not transmitted to the engine related element and the heat quantity of the burnt gas is increased.
Subsequently, the second burnt gas discharging means discharges the mixture gas of the above-described secondary gas and burnt gas. The burnt gas that has been discharged from the second gas burnt gas discharging means is fed to the exhaust passage upstream of the exhaust gas purifying catalyst through the second burnt gas passage. The mixture gas fed to the exhaust passage is introduced into the exhaust gas purifying catalyst through the exhaust passage.
In this case, since the above-described mixture gas has the heat quantity that is substantially equal to that of the burnt gas and has a lower temperature than that of the burnt gas, none of the second burnt gas discharging means, the second burnt gas passage and the burnt gas passage controlling means or the like are not excessively elevated. Furthermore, the exhaust gas purifying catalyst is elevated for a short period of time by the relatively large heat quantity possesses by the mixture gas.
The internal combustion engine with a combustion heater according to the present invention, the burnt gas passage controlling means may close the second burnt gas passage upon ignition and extinguishment of the combustion heater.
The reason for this is that, in the internal combustion engine with a combustion heater, it is expected that the pressure of the intake air supercharged by the supercharger is considerably high by the pressure of the exhaust gas, and in such a case, if the second burnt gas passage is communicated, the intake passage and the exhaust passage are in communication with each other through the combustion heater so that the amount of the intake air passing through the combustion heater is excessively increased to degrade the ignitability of the combustion heater.
On the other hand, in the internal combustion engine provided with the supercharger in the intake passage, in extinguishment, i.e., in the inoperative condition of the combustion heater, if the second burnt gas passage is communicated to thereby communicate the intake passage and the exhaust passage with each other, a part of the intake air supercharged by the supercharger is bypassed around the internal combustion engine to flow into the exhaust passage, resulting in degradation of the supercharging effect by the supercharger.
Next, an internal combustion engine with a combustion heater according to the present invention may comprise:
an exhaust gas purifying catalyst provided in an exhaust passage of the internal combustion engine for purifying harmful gaseous components contained in exhaust gas;
a combustion heater including a combustion chamber that is independent of the internal combustion engine and a heat exchange portion for transmitting to an engine related element heat held by burnt gas that has been burnt in the combustion chamber;
a first burnt gas discharging means for discharging from the combustion heater the burnt gas which has passed through the heat exchange portion;
a second burnt gas discharging means for discharging from the combustion heater the burnt gas that has not yet passed through the heat exchange portion or that has passed through a part of the heat exchange portion;
an intake air introducing passage for introducing air for combustion from an intake passage of the internal combustion engine to the combustion heater;
a first burnt gas passage for communicating the first burnt gas discharging means with a joint portion downstream of the intake air introducing passage in the intake passage;
a second burnt gas passage for communicating the second burnt gas discharging means with a joint portion downstream of the first burnt gas passage in the intake passage;
a third burnt gas passage for communicating the second burnt gas discharging means with the exhaust passage of the exhaust gas purifying catalyst; and
a burnt gas passage controlling means for controlling a flow of gas in the second burnt gas passage and the third burnt gas passage.
In this case, it is preferable that the joint portion between the intake passage and the second burnt gas passage and the joint portion between the exhaust passage and the third burnt gas passage are selected to a position where these pressures may be lower than that of the joint portion of the first burnt gas passage and that of the intake passage introducing passage in the intake passage.
Also, in the case where the supercharger is provided in the intake passage of the internal combustion engine, it is preferable to provide the intake air introducing passage downstream of the supercharger.
With such an arrangement, it is possible to selectively feed to the intake passage and the exhaust passage the gas that is high in heat quantity and lower in temperature than the burnt gas, without unstabilizing the combustion condition of the combustion chamber.
For instance, in the case where the temperature of the engine related element or the engine temperature is less than a predetermined temperature in start of the engine or the like, the burnt gas passage controlling means communicates the second burnt gas passage and at the same time closes the third burnt gas passage.
In this case, since the intake air introducing passage, the first burnt gas passage and the second burnt gas passage are in communication, applied to the combustion heater are the pressure in the vicinity of the joint portion of the intake air introducing passage in the intake passage, the pressure in the vicinity of the joint portion of the first burnt gas passage in the intake passage and the pressure in the vicinity of the joint portion of the second burnt gas passage in the intake passage.
The pressure in the vicinity of the joint portion of the second burnt gas passage in the intake passage is lower than the pressure in the vicinity of the joint portion of the intake air introducing passage in the intake passage and lower than the pressure in the vicinity of the joint portion of the first burnt gas passage in the intake passage. For this reason, the air for combustion is introduced from the intake passage through the intake air introducing passage to the combustion heater and at the same time the secondary air is introduced from the intake passage through the first burnt gas passage to the combustion heater.
The above-described air for combustion is introduced into the second burnt gas discharging means through the combustion chamber of the combustion heater. The above-described secondary air is caused to reversely flow through the heat exchange portion and to be introduced into the second burnt gas discharging means. Thus, if the secondary air is fed to the second burnt gas discharging means located downstream of the combustion chamber, even if the pressure difference between the joint portion of the second burnt gas passage and the joint portion of the intake air introducing passage in the intake passage is increased, the pressure difference between the upstream side and the downstream side of the combustion chamber is suppressed. As a result, the flow rate and the flow amount of the gas passing through the combustion chamber are not increased excessively and the combustion within the combustion chamber is stabilized.
Also, in the combustion heater, since the burnt gas that has been discharged from the combustion chamber is prevented from entering the heat exchange portion by the secondary air reversely flowing in the heat exchange portion, the heat of the burnt gas is not transmitted to the engine related element and the heat quantity of the burnt gas is increased..
Subsequently, the second burnt gas discharging means discharges the mixture gas of the above-described secondary gas and burnt gas. The burnt gas that has been discharged from the second burnt gas discharging means is fed to the intake passage through the second burnt gas passage. The mixture gas fed to the intake passage is introduced into the internal combustion engine through the intake passage.
In this case, since the above-described mixture gas has the heat quantity that is substantially equal to that of the burnt gas and has a lower temperature than that of the burnt gas, none of the second burnt gas discharging means, the second burnt gas passage and the burnt gas passage controlling means or the like are not excessively elevated. Furthermore, it is possible to keep the necessary amount of oxygen for the engine combustion by a large amount of oxygen contained in the secondary air in the mixture gas while elevating the temperature of the atmosphere within the sleeve of the internal combustion engine by the heat held by the burnt gas in the mixture gas. Thus, the startability of the engine is enhanced.
Incidentally, the internal combustion engine with a combustion heater according to the present invention may further comprise an intake throttle valve provided between a joint portion of the first burnt gas passage and a joint portion of the second burnt gas passage in the intake passage of the internal combustion engine for reducing a flow rate of intake air flowing through the intake passage in start of the internal combustion engine.
The reason for this is that, by operating the intake throttle valve at the start of the internal combustion engine, the pressure of the joint portion of the second burnt gas passage in the intake passage is lower than the pressure of the joint portion of the intake air introducing passage at the intake passage and lower than the pressure of the joint portion of the first burnt gas passage in the intake passage.
In the internal combustion engine with a combustion heater according to the present invention, the burnt gas passage controlling means closes the second burnt gas passage while communicating the third burnt gas passage when temperature elevation demand of the exhaust gas purifying catalyst occurs.
In this case, since the intake air introducing passage, the first burnt gas passage and the third burnt gas passage are in communication, applied to the combustion heater are the pressure in the vicinity of the joint portion of the intake air introducing passage in the intake passage, the pressure in the vicinity of the joint portion of the first burnt gas passage in the intake passage and the pressure in the vicinity of the joint portion of the third burnt gas passage in the exhaust passage.
The pressure in the vicinity of the joint portion of the third burnt gas passage in the exhaust passage is lower than the pressure in the vicinity of the joint portion of the intake air introducing passage in the intake passage and lower than the pressure in the vicinity of the joint portion of the first burnt gas passage in the intake passage. For this reason, the air for combustion is introduced from the intake passage through the intake air introducing passage to the combustion heater and at the same time the secondary air is introduced from the intake passage through the first burnt gas passage to the combustion heater.
The above-described air for combustion is introduced into the second burnt gas discharging means through the combustion chamber of the combustion heater. The above-described secondary air is caused to reversely flow through the heat exchange portion and to be introduced into the second burnt gas discharging means. Thus, if the secondary air is fed to the second burnt gas discharging means located downstream of the combustion chamber, even if the pressure difference between the joint portion of the third burnt gas passage and the joint portion of the intake air introducing passage in the intake passage is increased, the pressure difference between the upstream side and the downstream side of the combustion chamber is suppressed. As a result, the flow rate and the flow amount of the gas passing through the combustion chamber are not increased excessively and the combustion within the combustion chamber is stabilized.
Also, in the combustion heater, since the burnt gas that has been discharged from the combustion chamber is prevented from entering the heat exchange portion by the secondary air reversely flowing in the heat exchange portion, the heat of the burnt gas is not transmitted to the engine related element and the heat quantity of the burnt gas is increased.
Subsequently, the second burnt gas discharging means discharges the mixture gas of the above-described secondary gas and burnt gas. The burnt gas that has been discharged from the second burnt gas discharging means is fed to the exhaust passage through the third burnt gas passage. The mixture gas fed to the exhaust passage is introduced into the exhaust gas purifying catalyst through the exhaust passage.
In this case, since the above-described mixture gas has the heat quantity that is substantially equal to that of the burnt gas and has a lower temperature than that of the burnt gas, none of the second burnt gas discharging means, the third burnt gas passage and the burnt gas passage controlling means or the like are not excessively elevated. Furthermore, it is possible to elevate the exhaust gas purifying catalyst for a short period of time by the relatively large amount of heat of the mixture gas.
Incidentally, the internal combustion engine with a combustion heater according to the present invention may further comprise an intake throttle valve provided between a joint portion of the first burnt gas passage and a joint portion of the second burnt gas passage in the intake passage of the internal combustion engine for reducing a flow rate of intake air flowing through the intake passage when the temperature of the exhaust gas purifying catalyst is elevated.
The reason for this is that, in an internal combustion engine such as a diesel engine in which a combustion temperature is low in a low load operational region and an exhaust gas temperature is likely to be low, since there are cases that the exhaust purifying catalyst is cooled by the low temperature exhaust gas, it is necessary to reduce the exhaust gas amount to be discharged from the internal combustion engine so that the cooling caused by the exhaust is suppressed in order to elevate the temperature of the exhaust gas purifying catalyst.
On the other hand, the burnt gas passage controlling means may close the third burnt gas passage and may simultaneously communicate the second burnt gas passage when a temperature elevation demand of the exhaust gas catalyst provided in the exhaust passage of the internal combustion engine, occurs. Namely, in the case where the temperature of the exhaust gas purifying catalyst is to be elevated, by elevating the temperature of the intake air of the internal combustion engine, the temperature of the exhaust gas to be discharged from the internal combustion engine may be elevated, to thereby elevate the temperature of the exhaust purifying catalyst.
In this case, it is possible to reduce the amount of the air flowing through the intake passage by operating the throttle valve. The reason for this is that, since the air to be fed to the internal combustion engine through the intake passage and the mixture gas to be fed to the internal combustion engine from the combustion heater are included in the intake air to be fed to the internal combustion engine, if the amount of the air to be fed to the internal combustion engine through the intake passage is decreased, it is possible to sufficiently elevate the temperature of the intake air even with a small amount of the mixture gas and it is possible to reduce the fuel consumption rate needed for the operation of the combustion heater.
In the internal combustion engine with a combustion heater according to the present invention, the burnt gas passage controlling means may close the second burnt gas passage and the third burnt gas passage upon ignition and extinguishment of the combustion heater.